Andy Murray has revealed he burst into tears days after winning his Olympic gold medal when the enormity of what he had done finally sank in.

The Scot said: “I went to Toronto a couple of days afterwards. I’d been around people pretty much all the time since the final, and then when you’re on your own for a little while and you have a chance to think about what’s happened.

“It wasn’t just the Olympics, but what happened a few weeks beforehand as well, reaching the Wimbledon final. It was quite emotional.”

Murray, meanwhile, has backed Rafael Nadal to come back stronger than ever from the knee problems that may well sideline him for the rest of the year.

The Spaniard will now miss at least the next two months because of a partially torn tendon in his left knee.

He has been out since his shock loss to Lukas Rosol in the second round of Wimbledon, missing the Olympics and the US Open, and it is now definite he will miss Spain’s Davis Cup semi-final against the United States later this month.

Murray, though, has no doubt his friend and rival will return in good shape, saying “I’m sure he’ll come back strong.

“It might just take a little bit more time. He’s not really been out for really long periods of time beforehand. But he’s always come back to be one of the best players in the world. So I would expect the same this time.”

Serena Williams sent an ominous warning to her rivals with a 6-0 6-0 victory over Andrea Hlavackova to reach the quarter-finals of the US Open.

The fourth seed is now the favourite to win a fourth US Open crown at Flushing Meadows.